This invention relates to macromolecular monomers ("macromers" for brevity) of polyethers having a vinyl functional "head" group at one end, through which the macromer is polymerizable with a copolymerizable monomer, and a terminal hydroxyl (OH) group at the other end. The polymerization of the macromer generates a polymacromer with a polyvinyl backbone having polyether branches thus resulting in a graft or comb copolymer. Such polymerization of the macromer of this invention, to form comb copolymers, differs from graft copolymerization in the sequence of formation of the backbone relative to the formation of the graft unit.
The macromer is formed by cationic ring-opening polymerization of a cyclic ether ("CE") in conjunction with an alkenyl alcohol which functions as the generator of the propagating species, and a suitable cationic ring-opening catalyst. The alkenyl alcohol (referred to as the "propagator" because it functions as the propagating species (OH group) generator in the presence of a cationic initiator) may be substituted with substituents which do not interfere with the initiation, propagation and transfer reactions which generate the macromer in a polymerization which has the characteristics of a living polymerization. The macromer has substantially uniform molecular weight (mol wt) distribution such that the ratio of the weight average mol wt (Mw) to the number average mol wt (Mn) is not substantially above about 3, preferably less than 2.
It is to be noted that the macromers of this invention are formed by cationic ring-opening and not carbocationic polymerization, though both are classified as cationic polymerizations and often use the same cationic initiator. The cationic ring-opening involves the opening of strained rings of cyclic monomers and the propagating species is an oxonium, sulfonium or ammonium ion; carbocationic polymerization involves substituted olefinic monomers where the propagating species is a carbenium ion.
Numerous macromers of polytetrahydrofuran (polyTHF) have been synthesized by "living" cationic ring-opening polymerization involving an acrylic end group, inter alia, all by end-capping. But acrylic double bonds are quite different from allylic double bonds, and acrylic monomers are not cationically polymerizable (see Principles of Polymerization by G. Odian, Chap. 3, Table 3.1, McGraw Hill, New York 1970). Thus, hydroxyalkyl acrylates and methacrylates are unique chain transfer agents which are not cationically polymerizable (see U.S. Pat. No. Re. 31,468). There was no reason to expect that a monohydroxyl-terminated allyl propagator would remain intact under the conditions suitable for a cationic ring-opening polymerization.
To avoid the side reactions which interfere with the use of olefinic monomers, U.S. Pat. No. 4,327,201 to Kennedy and Fritsch teaches the formation of a poly(isobutylene) macromer with the use of vinyl benzyl halide and an allylic halide in conjunction with a variety of Lewis acid catalysts suited for cationic polymerization. In a later publication, Kennedy & Lo indicate concern over loss of a head group during synthesis, and found a specific catalyst which would avoid such loss. (see "Macromers by Carbocationic Polymerization II. An Improved Synthesis of Polyisobutenylstyrene and its Copolymerization with Methyl Methacrylate and Styrene" Polym. Reprint 23, No. 2 September '82).
Much effort has been directed to the preparation of various OH-terminated difunctional and polyfunctional polyethers by cationic ring-opening polymerization of a CE in conjunction with water or an alcohol or a diol or a polyol as disclosed in U.S. Pat. Nos. 3,129,232; 3,305,565; 3,850,856; 4,284,826; 4,077,991; 3,419,532; 3,402,169; 3,269,961; inter alia.
U.K. Patent Appln. No. 2,021,606A and U.S. Pat. No. 4,431,845 teach that OH-terminated poly(chloroalkylene ethers) have not proven entirely satisfactory when prepared by cationic ring-opening polymerization as disclosed in U.S. Pat. Nos. 3,850,856; 3,910,878; 3,3910,879; and, 3,980,579. Thus, the problems inherent in the use of prior art catalysts referred to in the foregoing U.S. patents have been documented. A solution to the problems was provided in the aforementioned U.S. Pat. No. 4,431,845. This solution was to use a catalyst comprising (i) a fluorinated acid catalyst having the formula H.sub.m XF.sub.n+m wherein X is selected from boron, phosphorus, arsenic and antimony, m is 0 or 1, and n is 3 when X is boron and n is 5 when X is phosphorus, arsenic and antimony, and, (ii) a polyvalent tin compound.
This patent reference teaches that only tin fluorometallic compounds even among other Group IV metals, has a peculiar catalytic action not attributable to Group V fluorometallic compounds. With this catalyst, it is suggested that any aliphatic OH-containing material such as a monomeric or polymeric mono- or polyhydric alkanol, haloalkanol or polymeric glycol having up to 6 OH groups, whether terminal or pendant, may be used in the formation of a polymer with an alkylene oxide, provided at least about 50% by weight (wt) of the alkylene oxide is a chloroalkylene oxide.
The reaction of a CE with an ethylenically unsaturated alcohol in the presence of a cationic catalyst is disclosed in U.S. Pat. Nos. 3,627,022 and 3,419,621 to yield a monoadduct, the addition of a single cyclic ether (oxirane) unit to the alcohol.
U.S. Pat. No. 4,485,211 to Okamoto discloses the use of a hydroxyl-containing material (HCM) having a single OH propagating site to form block copolymers of polyethers. The HCM may be an alkylene glycol such as ethylene glycol, or a prepolymer with plural OH propagating sites, such as poly(glycidyl ether) with 2 sites. U.S. Pat. No. 4,451,618 to Okamoto discloses the use of a hydroxyl-terminated prepolymer (HTP) with one or more OH end groups which also yield polyether block copolymers. With the emphasis on the essentiality of the OH propagating sites and the routine use of saturated end groups, the possibility that a vinyl group, and more specifically, an allylic end group might survive the conditions of cationic ring-opening polymerization simply escaped notice. In view of the large number of olefinically unsaturated monomers which undergo polymerization (see the list in Carbocationic Polymerization by Kennedy, J. P. and Marechal, E., Table 3.6, pp 37 et seq., John Wiley & Sons 1982) the fate of the double bond of the propagator seemed speculative.